Host cell oxidative responses can alter biomaterials and influence their long-term success. The initial reaction of neutrophils and monocytes with materials may influence the course of the inflammatory response. Previous work in our group has shown that both whole blood and monocytes from females showed a stronger oxidative burst to poly(dimethyl siloxane) PDMS than did whole blood and monocytes from males. The inflammatory response in male and female Balb/c mice to subcutaneous PDMS is being evaluated in an ongoing study. ESCA and SIMS will be used to characterize the PDMS materials.